The present invention is directed to methods and devices for removing material in procedures such as atherectomy and endarterectomy. Atherectomy, for example, is performed to remove plaque from blood vessels to open obstructed vessels and improve blood flow.
The present invention is directed to improved devices and methods for removing material from a vascular site.
The present invention provides devices and methods for removing material from a vascular site. The device has an expandable cage which forms a number of openings when expanded. The cage is expanded at the desired site for removing material so that unwanted material extends into the openings. A material removing element is then used to remove material extending into the openings.
The openings in the cage are preferably formed by rigidly connected elements which form a frame around the openings. The rigid frame elastically deforms when the cage is collapsed so that upon release of the collapsed cage, the elastic response of the cage urges the material into the openings. The cage is preferably made of integrally formed elements and may be made of stainless steel or a superelastic material. The cage is preferably held in the collapsed position by a sheath which is retracted to expose the cage and permit the cage to expand. Although the sheath is a preferred structure to collapse the cage, any other structure may be used. The cage may also be expanded utilizing the shape memory characteristics of a shape memory material. The cage may also be vibrated using an ultrasound generator to help the cage penetrate the material to be removed
In an aspect of the invention, the cage preferably forms 2-20 openings, more preferably 4-8 openings, which are spaced around the device. An advantage of the present invention is that the user does not need to rotate the device to orient a single cutting window. The openings preferably have a size of at least 0.5 mm2 when expanded and have a length of at least 0.040 inch. The size of the opening is defined by the surface area of an imaginary surface extending between the rigidly connected elements. The length is the longest distance within the opening when measured in the direction of the longitudinal axis of the device. The preferred size and number of openings is particularly suited for atherectomy in the coronary arteries, however, other configurations and sizes may be used without departing from the scope of the invention.
The material removing element may remove the material with any suitable method and a preferred method is to cut the material. The expanded shape of the material removing element is preferably larger than the expanded inner surface of the cage so that the material removing element is urged against the interior surface of the cage. The material extending into and through the openings is sheared by shearing surfaces on the cage and removal element. The material removing element preferably removes material around a significant portion of the cage but may also selectively remove material extending into the openings.
In still another aspect of the present invention, the device may also have a flexible bag which receives the material which has been removed. The bag is preferably attached to the material removing element so that the bag is deployed behind the removing element as the removing element is advanced through the cage. The device may also simply trap the material within the cage and/or material removing element, rather than using the bag, or may use a suction lumen or a capsule in the tip or shaft to trap the material. Thus, although it is preferred to use the bag, any other method of retrieving the material may be used without departing from the scope of the invention.
In accordance with a method of the present invention, an expandable cage is introduced into a vessel. The method is described in connection with the preferred embodiments, however, the method may be practiced with other devices without departing from the scope of the invention. The cage is expanded within the vessel so that material to be removed, such as plaque, extends into the openings. The material removing element is then used to remove the material. The cage protects healthy tissue by limiting the amount of material which is removed. The cage also preferably guides movement of the material removing element, however, this feature may not be essential depending upon the particular removal method used.
In yet another aspect of the invention, the present invention is also directed to a method of removing neo-intimal tissue and other material from the inside of a previously deployed stent. The present invention is particularly useful for this procedure since the cage prevents the material removing element from contacting the stent.
In still another aspect of the present invention, the cage is left within the vessel to hold the vessel open after the procedure.